A fellow inmate at a labor camp attacked Paul Whelan, a former businessman US Marine imprisoned in Russia, CBS News reported Tuesday.

Whelan is serving a 16-year sentence at the said labor camp. Whelan’s brother, David Whelan, confirmed the incident in an email where he detailed a phone call Paul made to their parents, according to CBS. During his work at a sewing table in the camp, Paul reportedly encountered interference from another prisoner on the production line.

After the inmate repeatedly ignored Whelan’s request to move, the situation escalated into a physical altercation. “The prisoner hit Paul in the face, breaking Paul’s glasses in the process, and attempted to hit him a second time,” David wrote, per CBS. “Paul stood up to block the second hit and other prisoners intervened to prevent the prisoner continuing to attack Paul.”

Paul Whelan, the American businessman who the U.S. considers to be wrongfully detained by Russia, was attacked Tuesday by a fellow prisoner at the labor camp where he is serving a 16-year sentence, according to his family. https://t.co/8grW2FErSJ

— CBS News (@CBSNews) November 28, 2023

“These sorts of attacks can occur any time and, due to the various sharp implements in the workshop including the shears the other prisoner was holding today, could escalate into a far more serious attack,” David added, per CBS. (RELATED: American Journalist Jailed In Russia Has Detention Extended After Secret Hearing)

Paul’s parents drew attention to the matter by sharing an audio recording of the call with U.S. authorities, including the State Department and National Security Council, urging them to address his safety with the Russian government, CBS reported.

“We call on Russia to ensure Paul Whelan and all U.S. citizen detainees are safe,” the State Department spokesperson told CBS in a statement. “We urge the Russian government to ensure fair treatment and appropriate medical care for all U.S. citizens detained in Russia. Russia should immediately release Paul Whelan.”

Russia arrested Paul and accused him of spying in 2018. He claims he was only in Russia to attend a wedding and denies the accusations, CBS noted. Russia convicted David in 2020, and he has since been confined to a labor camp in Mordovia.